This invention relates to seals for pipe connections and more particularly to replaceable metal seals for oilfield connections.
In subterranean oil and gas well applications, it is necessary to couple various sections of pipe together. In securing a pipe joint, it is desirable to provide a seal at the connection to prevent fluid flow. Threaded connections often maintain pressure differentials thereacross. The most common method of providing fluid and pressure integrity is to use elastomeric O-rings to seal the interface of the tubular members adjacent the threaded connection. However, increased drilling depths with greater down-hole pressures have caused the industry to request metal-to-metal seals between tubular members and associated components joined by threaded connections in a production or completion casing string. Normally, such metal-to-metal seals are machined into either the pin or box of the connection. Where the metal-to-metal seals have been machined into the steel members of the connection, it is often impossible to refurbish the metal-to-metal seal after retrieving that portion of the connection, either pin or box, on which the seal was machined. Any "ding", blemish, scoring, or corrosion of the metal-to-metal seal will cause the seal to be unusable thus requiring a new pipe joint or tool since the metal-to-metal seal cannot be refurbished or replaced. This is particularly expensive where the metal-to-metal seal is for the connection of a running tool, run-in and tie-back tool, tie-back tool or other oilfield tool. If the metal-to-metal seal could be refurbished or replaced, one tool for a particular size connection could be used with several strings merely by refurbishing or replacing the metal-to-metal seal.
U.S. Pat. No. 2,918,315 to Peter et al. discloses a metal-to-metal seal for sealing the connection between male and female members at the surface. The metal-to-metal seal includes a ring heated to expand its inner diameter for seating on the male pipe member. The female pipe member is threaded onto the male member so that the terminal end of the female member abuts the annular surface of the ring. The terminal end of the female member is then welded to the ring, which in turn, is cooled so that the ring is shrink fitted onto the male member.
U.S. Pat. No. 3,668,754 to Boast shows a non-oilfield pipe joint formed between a male pipe member and a female pipe member in which an independent annular element is heated in order to be positioned on the outer surface of the male member, and is subsequently cooled to shrink onto the pipe in intimate fitting engagement with projections and recesses on the male pipe member. A flange on the female pipe member engages the annular element to secure the fitting.
U.S. Pat. No. 4,537,406 to Hirasuna et al. discloses a seal assembly formed by disposing an annular shape memory material combined with a compliant seal within the counterbore of a female pipe member, disposing the male member in the counterbore and thereafter activating the annular member by threading the male and female members together to permit the annular member to assume its memory shape configuration, in which it forms a pressure and fluid-tight seal.
U.S. Pat. No. 4,601,498 to Hauoen discloses a metal-to-metal seal for a subterranean well tool in which an annular deformable metallic sleeve is placed about the terminal end of a male pipe member prior to threaded insertion of the male member into a recess in a female member.
U.S. Pat. Nos. 2,539,057; 3,166,345; 3,275,348; 3,382,563; 3,998,479; and 4,793,382 disclose other seals for threaded connections.
The principal deficiency of the prior art metal-to-metal seals are that they are normally machined into the metal body of one of the members of the connection and thus cannot be refurbished or replaced once damaged. Other connections with metal seal rings cannot be completed at a remote location. The present invention overcomes the deficiencies of these prior art sealed connections.